This is the first time that I chose a mobile phone without a numeric keypad, and I would say it really brings some inconvenience.
First of all, if you want to find a phone book entry from the address book, you will miss the numeric keypad. For example, when you want to search for a friend with a name that begins with "S" you have no short cut. Of course, for most of the time, you will only call a small subset of people, you can easily locate them from the recent dial list. And for other less called numbers, you can also use the stylus to write.
And here comes another problem. Actually, when I was using Palm OS, I always wonder why there's a special area for writing, especially when full screen writing is supported. Now I understand why! Suppose I wanted to write by the stylus, I have first change the input mode! And this mode changing action requires several clicks on the screen, and that's troublesome enough when you just want to enter a single letter, in order to speed up the searching! That really defeat the purpose, it's just not speed up.
Another usage on the numeric keypad is quick dial. With my more traditional phones, I can always define several numbers which I always call, and then I can make a call by simply press and hold a single button!
Frankly, I guess all these could be solved, for example, by defining different way of this quick dial by using the stylus. Or even simpler, to make the button on the touch screen bigger!